1. Field of the Invention
The present invention relates to a method of generating a current trajectory for seek control of a hard disc drive and a seek control system using the same, and more particularly, to a method of generating a current trajectory by which power is reduced during seek control of a hard disc drive, and a seek control system using the same.
2. Description of the Related Art
In general, a hard disc drive comprises a plurality of magnetic transducers that sense magnetic field of and/or magnetize a single rotating disc or each of a plurality of rotating discs, to write and/or read information to and/or from the disc. The information is typically formatted in a plurality of sectors placed in a ring-shaped track. The tracks are numbered across a surface of the disc. The track numbers being vertically similar to one another are called cylinders. Thus, each track is defined by a cylinder number.
In general, each transducer is integrated to a slider included in a head gimbal assembly (HGA). Each HGA is attached to an actuator. The actuator has a voice coil adjacent to a magnetic assembly, which also specifies a voice coil motor (VCM).
The hard disc drive also comprises a driving circuit for supplying a current to excite the VCM, and a controller. The excited VCM rotates the actuator and moves the magnetic transducers across the surface of the disc(s).
When information is written and/or read into and/or from the disc, the hard disc drive performs a seek routine for moving the magnetic transducers from one cylinder to another cylinder. During the seek routine, the VCM is excited by a current used to move the magnetic transducers to a position of a new cylinder from the surface of the disc. The controller performs a servo routine that guarantees the magnetic transducers to accurately move to a correct position of a cylinder at the center of a track.
Many studies on moving the magnetic transducers to a correct position within the shortest time during the seek routine have been made. However, a serious problem is power consumption of a hard disc drive mounted on a mobile device such as a camcorder or a MP3 player. Since a system in a mobile device is powered by a battery, the power consumption should be as small as possible. The power consumption can be reduced by scheduling operation or stop of a drive by an application program during execution of the application program, by driving a spindle motor, and by appropriately performing a seek control of the VCM.
As described above, the conventional seek control of the VCM has been focused on optimum time control, so as to minimize a track seek time. However, since an acceleration waveform is discontinuous, the optimum time control stimulates a high frequency mode of a mechanical system and increases undesired mechanical noise and vibration. Due to this problem, a seek controller using a soft acceleration waveform of a sinusoidal wave shape, instead of a square wave shape, has been used.
However, a hard disc employed in a mobile device should focus on reducing power consumption rather than on reducing seek time and noise. In particular, during a random file access, the amount of the power consumption during the seek control is not negligible. Accordingly, the hard disc drive used in the mobile device requires a control by which at least required seek time performance is maintained while power consumption is minimized.